Isupov Michail N, Lebedev Andrey A
Henry Wellcome Building for Biocatalysis, School of Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, England.
Acta Crystallogr D Biol Crystallogr. 2008 Jan;64(Pt 1):90-8. doi: 10.1107/S0907444907053802. Epub 2007 Dec 5.
The efficiency of the cross-rotation function step of molecular replacement (MR) is intrinsically limited as it uses only a fraction of the Patterson vectors. Along with general techniques extending the boundaries of the method, there are approaches that utilize specific features of a given structure. In special cases, where the directions of noncrystallographic symmetry axes can be unambiguously derived from the self-rotation function and the structure of the homologue protein is available in a related oligomeric state, the cross-rotation function step of MR can be omitted. In such cases, a small number of yet unknown parameters defining the orientation of the oligomer and/or its internal organization can be optimized using an exhaustive search. Three difficult MR cases are reported in which these parameters were determined and the oligomer was positioned according to the maximal value of the correlation coefficient in a series of translation searches.
分子置换（MR）中交叉旋转函数步骤的效率本质上是有限的，因为它仅使用了一部分帕特森向量。除了扩展该方法边界的通用技术外，还有利用给定结构特定特征的方法。在特殊情况下，如果非晶体学对称轴的方向可以从自旋转函数中明确推导出来，并且同源蛋白的结构在相关的寡聚状态下可用，那么MR的交叉旋转函数步骤可以省略。在这种情况下，可以使用穷举搜索来优化定义寡聚体方向和/或其内部组织的少数未知参数。报道了三个困难的MR案例，其中确定了这些参数，并根据一系列平移搜索中相关系数的最大值对寡聚体进行了定位。
